Aquifer Structuring and Hydrogeological Investigation in North African Regions Using Geophysical Methods: Case Study of the Aquifer System in the Kairouan Plain (Central Tunisia)

Abstract

This study presents an integrated methodology to characterize the aquifer structuring, and geometry in the case of geological complexity and lack of hydrogeological data. Gravity methods analysis, seismic reflection, wireline logging, and electrical resistivity tomography techniques are used to identify the lithological and geometrical knowledge of the Mio-Plio-Quaternary aquifer in the Kairouan plain. In the Kairouan region, the Mio-Plio-Quaternary series form a complex aquifer system formed by siliciclastic fluvio–deltaic deposits. It consists of sandy and sandy clay horizons interbedded with clay levels. The geometry of the Mio-Plio-Quaternary systems is not yet precisely defined. The present study is dealing with the hydrogeological properties of these deeper sand layer reservoirs in the Kairouan basin using an integrated geophysical approach. Gravity is used in order to define regional structuring, which is characterized by the presence of a deep fault corridor. The interpretation of wireline logging of 15 petroleum wells shows that the Mio-Pliocene deposits (Ségui Formation) contain five reservoirs. The interpretation of fourteen 2D seismic reflection profiles is used to characterize the aquifer structuring and to identify the major aquifer boundaries. The Kairouan plain is marked in the subsurface by the presence of platforms, anticlines, synclines, and grabens: the Sidi El Hani and Chorbane blocks are separated by master deep-seated faults corridor directed N90 to N120. The groundwater flow and the water resources evolution are deduced from the water level in 26 piezometres in 2013 and monthly water level measurements in 4 monitoring wells during the 1968–2013 period.